wavy channel (Figure 5-2) from the streamline plot and the velocity profile, and this agrees very
well with the results from the analytical solution developed in Chapter 4. In both cases, the
dimensionless parameter K is 2.
Further comparison are made between the simulated stream function and electric potential
data from CFD-ACE+ and the calculated data from the analytical solution. Electric potential
values at 122 locations inside the wavy channel are extracted from the simulated flow, and then
normalized to be in the range of 0 to 1. Another set of data are calculated at the same locations
but using the analytical solution. To compare the two sets of electric potential data, Figure 5-3a
is generated with the pair of simulated and calculated data as the x and y coordinates,
respectively. Similarly, Figure 5-3b is generated based on the stream function data from the
CFD simulation and the analytical solution. The near perfect linear relation in both plots
suggests the good match between these two solutions, hence CFD-ACE+ is capable of
simulating electroosmosis and yielding valid solution to flow recirculation in microchannels.
5.2.2 Modeling of Ridged Channels
A small portion of ridged channels is modeled using CFD-MICROMESH. Given the mask
layout (Figure 5-4a), etching properties isotropicc) and desired etching depth (40 micron), the
software simulates the etching process, generates the ridged channel model and subsequently
meshes it with specified type of meshing algorithm. Figure 5-4b shows the resulting simulation
model. The geometry of the ridge structure, same as the ridged channel from which the image
(Figure 5-1) is acquired. The model, containing 11 ridge structures, has 907,889 cells (prisms
and hexahedra) and 738,236 nodes. The typical length scale of an average cell structure is about
1 micron.
The fluid properties and the boundary conditions, including the pressure and the electric
potential at both ends, and the zeta potential at the walls, are properly defined. Finite volume